Curiosity - CA vs OA how are these different

[Cpapian]

I'm a newb but I think I know the answer to this one.  When you are having the apnea event the machine sends a pressure pulse to test your airway.  If the pulse is blocked by an obstruction in your airway it knows the event is obstructive apnea.  If the pulse flows freely into your lungs then it classifies it as a clear airway / central apnea event.

But.....it’s often the case that there is no flow limit (see the flow limit chart)—so no obstruction is being picked up—but the events are still evaluated as OAs.

At least half my events labeled OA have no contemporaneous flow limit.

I have exactly the same questions as Cpapier, and I don’t want to hog this thread.

 Not to worry.  We are both newbies and both of us are trying to learn more.

How  all of these little pieces of the puzzle work together is interesting.

[Cpapian]

lets get your min pressure up to 10 and help with events before they even get started. I'd also raise the max to 15 and give some head space.
next is to fix what I think could be mouth breathing, from your tidal volume of 320. Do all the stuff they discuss and get some charts up. If that doesn't work to get up around, for an average build 500 with a good chart, get a FFM


edit, Just noticed you are a female, 320 can be ok of you are short and small framed. it would need to look at the charts to see if there are indicators

what I'm seeing is a few deep breaths after the OA and a slow return to normal after the CA. both are typical for oa and ca
Some CA are/can be just your body regulating your o2/co2 balance as a new cpap users and will settle within 12 weeks.

Tidal volume that's interesting.   I have been wondering for a while how I can tell if it is good or not.  For me - 320 to 440 is my usual range.  I am 5'4"  not sure if that is considered short.  I spend a lot of time sleeping on my stomach.  Don't know if that could affect the tidal volume.  I haven't come anywhere near to understanding tidal volume implications in context of the whole process.  I have read the wiki and understand that it is the amount of air that passes in and out of the lungs, but never knew what amount should be.  Interesting

[ajack]

This will give an indication of volume, with a 100ml swing on the median, I would suggest there could be some mouthbreathing. Your breath per minute is 14 and not too bad, so you aren't breathing rapidly to make up the shortfall. search the site, there are lots of threads on it. ask more questions as needed.

[DeepBreathing]

There's a brief explanation along with some videos of OA and CA on the Resmed site. (You need to scroll down).

https://www.resmed.com/us/en/commercial-...ology.html  

Also here:  

https://www.resmed.com/au/en/commercial-...ology.html

Central sleep apnea (CSA) detection uses the Forced Oscillation Technique (FOT) to determine a whether a patient’s airway is open or closed during an apnea. When an apnea has been detected, small oscillations in pressure (1 cm H2O peak-to-peak at 4 Hz) are added to the current device pressure. The CSA detection algorithm uses the resulting flow and pressure (determined at the mask) to measure whether the airway is open or closed.

In the charts which CPapian posted there is very little visible difference between the OA and CA. If you look closely in both cases you can see the flow line oscillating during the apnea. The FOT is very clever but it's not foolproof and mistakes can occur - usually false positives for central apnea. Typically with an obstructive apnea there is a very large recovery breath at the end of the apnea which shows as a distinct spike in the chart - this only shows up to a minor extent in CPapian's charts.

[DeepBreathing]

Following up the question about flow limitations, these videos explain it pretty well:

https://www.youtube.com/watch?v=8mPHMHRh-_o

https://www.youtube.com/watch?v=3Ehb7U78P5w

You can see that flow limitation is part of a continuum from normal breathing through FL, hypopnea and obstructive apnea.

[TBMx]

in the cilinical manual for ResMed there are some nice pictures which show the difference (regarding how the machine detects it).

In technical terms: if you have (even a small) leak the machine can confuse any apnea with a CA.
If you have a nasal mask and are able to close down the nasal-passage (meaning breath freely through your mouth under pressure) that will show up as an OA (of course) (as will "sometimes" swallowing)

[Cpapian]

This will give an indication of volume, with a 100ml swing on the median, I would suggest there could be some mouthbreathing. Your breath per minute is 14 and not too bad, so you aren't breathing rapidly to make up the shortfall. search the site, there are lots of threads on it. ask more questions as needed.

Last night I didn't fall asleep for a while.  I stopped the machine, got up and did stuff.  The 35 minutes of the first session look like this.    Tidal volume was 460.  Which is a big difference from my sleeping Tidal Volume.  I notice none of my breaths look like those nice tidy breaths I see on the charts.

[Cpapian]

   to everyone who has contributed.  I am looking over the information/links provided and will try to digest and explore these new aspects vis a vis my charts.  I must be a nerd because I find this fascinating.

[Timur]

That makes me a nerd as well! I love learning about all of this ....  it has sort of developed into a bit of an obsession .... er, sorry, interest of mine now to read as much as I can about sleep apnea, as much recent research as I can lay my hands on ... and analyzing  SH charts etc etc.    

Looking at other people's data is fascinating to me as well. 


BTW, my median tidal volume in SH over the past year has been 340. I'm short, just shy of 5ft. Very physically active and have no lung issues. Height and gender influence tidal volume a lot.

[Sleeprider]

Both apnea events look the same to me. The machine in your case makes the call based on forced oscillation technique (FOT). Since the machine cannot measure chest effort which defines the difference between OA and CA, it is based on the return wave to the sensor from FOT. There is always some doubt about the accuracy of this method. Although it is based on considerable research and is accurate for most people, most of the time, it is not infallible. I actually think both of these examples are CA, especially with the OA being recorded just before you awaken and end the session.